1. Field of the Invention
This invention relates to an apparatus for opening and closing a working area of a machine tool such as an NC lathe, and is applicable to a machine tool having two doors for opening and closing an operation opening formed in a cover to enable and inhibit the access to the working area.
2. Description of Related Art
In general, NC lathes are so constructed that a cover is provided to separate, as a partition, the working area from an operator. The cover is formed with an opening through which the operator can attach and detach a workpiece. The opening is opened and closed with a front door. Some lathes are further provided with a ceiling shutter which covers an upper part of the working area, and which can be opened to facilitate the access to a tool post or a chuck for preparation by the operator. Each of these front door and ceiling shutter is generally opened and closed manually by the operator.
In case where two doors such as the front door and the ceiling shutter are provided, detection switches are provided for respectively detecting the closed conditions of the doors, so that the lathe will not be able to work unless both the front door and the ceiling shutter are closed.
The structure having the front door and the ceiling shutter and provided with respective detection switches requires a larger number of switches and addition or modification of sequence circuits, and thus results in the increased cost as compared with the structure in which the ceiling shutter is not present.
The present invention is made in view of the above drawbacks. It is an object of the present invention to provide a cost-effective apparatus for opening and closing a working area of a machine tool, which is free from the addition of the closed condition detection switch and the need of adding or modifying the sequence circuits.
To achieve the above-noted object, the present invention provides an apparatus for opening and closing a working area of a machine tool having a cover separating the working area from an operator. The apparatus comprises two doors for opening and closing an operation opening formed in the cover, a detection switch for detecting a closed condition of either one of the doors, and an interlocking mechanism which is adapted to block a closing operation of the one door while the other door is open.
In the apparatus for opening and closing the working area of the machine tool according to the present invention, a detection switch is provided for detecting a closed condition of one of the doors, and the one of the doors is unable to be closed by the interlocking mechanism when the other door is open. Therefore, the detection of the closed condition on the one door means the detection of the closed conditions on both of the doors, and accordingly, only one detection switch is enough to detect the closed conditions of both the doors. Consequently, it is possible to obviate the necessity of adding and modifying the sequence circuits and avoiding the increase of the cost.
The present disclosure relates to the subject matter contained in Japanese patent application No. Hei. 10-275248 (filed on Sep. 29, 1998), which is expressly incorporated herein by reference in its entirety.